10
THE BIOLOGY OF EUPHAUSIIDS
near the Shetland Islands. As a result of these, Thysanopoda norvegica
was added to the list of British fauna. He captured young specimens
in a net fishing a t the surface of the sea a t the Outer Skerries in 1861,
but only one specimen was sufficiently adult to identify and this was a
maIe, not previously described by Sars. Michael Sars's even more
distinguished son, George Ossian Sars, recorded the species several times
near the Norwegian coasts and then, in a report on the Crustacea
collected by the Norwegian expedition on 1876 in the area 61" to
66"N and 6"36'E to 10"21'W, known as the Norwegian sea and lying
between Norway and Iceland, he included Thysanopoda norvegica as the
only euphausiid in his list of Schizopoda. The species was found in
numerous places both a t great depths and swarming a t the surface, and
larvae a t various developmental stages were studied. I n his report,
G. 0. Sars (1877) was by this time able to state that the species occurred
not only off the Norwegian coasts but also near the Lofoten Islands,
Finmark, East Greenland, and the Polar Sea off the coast of Nova
Zemlya. He listed it as absent from Spitzbergen, West Greenland, and
other polar islands. The next step forward in the classification of
Thysanopoda norvegica came in G. 0. Sars's (1883b) preliminary report
on the Schizopoda collected during the World's first great oceanographic
expedition round the world, that of H.M.S. " Challenger ') during the
years 1873-76. He described a new euphausiid genus Nyctiphanes mainly
characterized by the peculiar rejlexed leaflet on the antennular peduncle, as
well as by the structure of the last two pairs of (thoracic) legs, both of which
are reduced, the last pair showing no trace of its outer branch, the
exopodite. Actually, as will be presently learnt, Holt and Tattersall
(1905a) noted that in both sexes of Nyctiphanes norvegica, exopodites
were present on the seventh thoracic limbs. Into this genus Sars
gathered Thysanopoda couchii (Bell), T . norvegica M. Sars and a new
species from the southern hemisphere, Nyctiphanes australis G. 0. Sars.
These three species thus became known as Nyctiphanes couchii (Bell),
N . norvegica (M. Sars) and N . australis G. 0. Sars.
G. 0. Sars (1885), in his full report on the " Challenger " Schizopoda,
even went so far as to suggest that Thysanopoda norvegica M. Sars was
perhaps identical with T . couchii Bell and that it belonged with
Nyctiphanes australis in the genus Nyctiphanes. This is rather surprising
and it can only be assumed that so careful an observer as Sars did not
have the opportunity to examine N . couchii closely or he would certainly
not have confused it with N . norvegica. Nevertheless, confusion of the
two species was further perpetuated by Lo Bianco (1901, 1904) who
gave a description of N . norvegica and illustrated it with a picture of
N . couchii, as Tattersall (1909) subsequently pointed out. Further
THE BIOLOGY OF EUPHAUSIIDS
near the Shetland Islands. As a result of these, Thysanopoda norvegica
was added to the list of British fauna. He captured young specimens
in a net fishing a t the surface of the sea a t the Outer Skerries in 1861,
but only one specimen was sufficiently adult to identify and this was a
maIe, not previously described by Sars. Michael Sars's even more
distinguished son, George Ossian Sars, recorded the species several times
near the Norwegian coasts and then, in a report on the Crustacea
collected by the Norwegian expedition on 1876 in the area 61" to
66"N and 6"36'E to 10"21'W, known as the Norwegian sea and lying
between Norway and Iceland, he included Thysanopoda norvegica as the
only euphausiid in his list of Schizopoda. The species was found in
numerous places both a t great depths and swarming a t the surface, and
larvae a t various developmental stages were studied. I n his report,
G. 0. Sars (1877) was by this time able to state that the species occurred
not only off the Norwegian coasts but also near the Lofoten Islands,
Finmark, East Greenland, and the Polar Sea off the coast of Nova
Zemlya. He listed it as absent from Spitzbergen, West Greenland, and
other polar islands. The next step forward in the classification of
Thysanopoda norvegica came in G. 0. Sars's (1883b) preliminary report
on the Schizopoda collected during the World's first great oceanographic
expedition round the world, that of H.M.S. " Challenger ') during the
years 1873-76. He described a new euphausiid genus Nyctiphanes mainly
characterized by the peculiar rejlexed leaflet on the antennular peduncle, as
well as by the structure of the last two pairs of (thoracic) legs, both of which
are reduced, the last pair showing no trace of its outer branch, the
exopodite. Actually, as will be presently learnt, Holt and Tattersall
(1905a) noted that in both sexes of Nyctiphanes norvegica, exopodites
were present on the seventh thoracic limbs. Into this genus Sars
gathered Thysanopoda couchii (Bell), T . norvegica M. Sars and a new
species from the southern hemisphere, Nyctiphanes australis G. 0. Sars.
These three species thus became known as Nyctiphanes couchii (Bell),
N . norvegica (M. Sars) and N . australis G. 0. Sars.
G. 0. Sars (1885), in his full report on the " Challenger " Schizopoda,
even went so far as to suggest that Thysanopoda norvegica M. Sars was
perhaps identical with T . couchii Bell and that it belonged with
Nyctiphanes australis in the genus Nyctiphanes. This is rather surprising
and it can only be assumed that so careful an observer as Sars did not
have the opportunity to examine N . couchii closely or he would certainly
not have confused it with N . norvegica. Nevertheless, confusion of the
two species was further perpetuated by Lo Bianco (1901, 1904) who
gave a description of N . norvegica and illustrated it with a picture of
N . couchii, as Tattersall (1909) subsequently pointed out. Further